public class HashBuck {

    static class Node{
        public int key;
        public int val;
        public Node next;

        public Node(int key, int val) {
            this.key = key;
            this.val = val;
        }
    }
    public Node[] array;

    public int usedSize;

    public static final double LOADFACTOR = 0.75;

    public HashBuck() {
        array = new Node[8];
    }

    public void put(int key,int val) {
        int index = key % array.length;
        Node cur = array[index];
        while (cur != null) {
            if (cur.key == key) {
                cur.val = val;
                return;
            }
            cur = cur.next;
        }
        //采用头插法进行插入
        Node node = new Node(key, val);
        node.next = array[index];
        array[index] = node;
        usedSize++;
        if (calculateLoadFactor() >= LOADFACTOR) {
            //扩容
            resize();

        }
    }

    private void resize() {
        Node[] newArray = new Node[2*array.length];

        for (int i = 0; i < array.length; i++) {
            Node cur = array[i];
            while (cur != null) {
                Node curNext = cur.next;
                int index = cur.key % newArray.length;//找到了在新数组当中的位置
                cur.next = newArray[index];
                cur = curNext;
              }
        }
        array = newArray;
    }

    //计算负载因子
    private double calculateLoadFactor()  {
        return usedSize*1.0 / array.length;
    }

    public int get(int key) {
        int index = key % array.length;
        Node cur = array[index];
        while (cur != null) {
            if (cur.key == key) {
                return cur.val;
            }
            cur = cur.next;
        }
        return -1;
    }
}
